Structured light methods are widely used as non-contact 3D scanners. Common applications of this technology are industrial inspection, medical imaging, and cultural heritage preservation. These scanners use one or more cameras to image the scene while being illuminated by a sequence of known patterns. One projector and a single camera is a typical setup, where the projector projects a fixed pattern sequence while the camera records one image for each projected pattern. The pattern sequence helps to establish correspondences between projector and camera coordinates. Such correspondences in conjunction with a triangulation method allow recovery of the scene shape. The pattern set determines many properties of a structured light 3D scanner such as precision and scanning time.
A general purpose 3D scanner must produce high quality results for a variety of materials and shapes to be of practical use. In particular, the general purpose 3D scanner must be robust to global illumination effects and source illumination defocus, or measurement errors would render the general purpose 3D scanner unsuitable for scanning non-Lambertian surfaces. Global illumination is defined as all light contributions measured at a surface point not directly received from the primary light source. Common examples are interreflections and subsurface scattering. Illumination defocus is caused by the light source finite depth of field. It is known that high frequency structured light patterns are robust to such issues.
However, most existing structured light based scanners are not robust to global illumination and defocus effects, and a few that are robust either use pattern sequences of hundreds of images, or fail to provide a closed form decoding algorithm. In both cases, the existing structured light based scanners cannot measure scene shapes as fast as required by many applications.